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Differential acetylcholine and GABA release from cultured chick retina cells
Author(s) -
Santos Paulo F.,
Carvalho Ana L.,
Carvalho Arsélio P.,
Duarte Carlos B.
Publication year - 1998
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1998.00281.x
Subject(s) - acetylcholine , chemistry , cholinergic , choline acetyltransferase , gabaergic , nitrendipine , tetrodotoxin , neurotransmitter , calcium , neuroscience , biophysics , endocrinology , biochemistry , biology , receptor , organic chemistry
In the present work we investigated the mechanisms controlling the release of acetylcholine (ACh) and of γ‐aminobutyric acid (GABA) from cultures of amacrine‐like neurons, containing a subpopulation of cells which are simultaneously GABAergic and cholinergic. We found that 81.2 ± 2.8% of the cells present in the culture were stained immunocytochemically with an antibody against choline acetyltransferase, and 38.5 ± 4.8% of the cells were stained with an antibody against GABA. Most of the cells containing GABA (87.0 ± 2.9%) were cholinergic. The release of acetylcholine and GABA was mostly Ca 2+ ‐dependent, although a significant release of [ 3 H]GABA occurred by reversal of its transporter. Potassium evoked the Ca 2+ ‐dependent release of [ 3 H]GABA and [ 3 H]acetylcholine, with EC 50 of 31.0 ± 1.0 m m and 21.6 ± 1.1 m m , respectively. The Ca 2+ ‐dependent release of [ 3 H]acetylcholine was significantly inhibited by 1 μ m tetrodotoxin and by low (30 n m ) ω‐conotoxin GVIA (ω‐CgTx GVIA) concentrations, or by high (300 n m ) nitrendipine (Nit) concentrations. On the contrary, the release of [ 14 C]GABA was reduced by 30 n m nitrendipine, or by 500 n m ω‐CgTx GVIA, but not by this toxin at 30 n m . The release of either transmitters was unaffected by 200 n m ω‐Agatoxin IVA (ω‐Aga IVA), a toxin that blocks P/Q‐type voltage‐sensitive Ca 2+ channels (VSCC). The results show that Ca 2+ ‐influx through ω‐CgTx GVIA‐sensitive N‐type VSCC and through Nit‐sensitive L‐type VSCC induce the release of ACh and GABA. However, the significant differences observed regarding the Ca 2+ channels involved in the release of each neurotransmitter suggest that in amacrine‐like neurons containing simultaneously GABA and acetylcholine the two neurotransmitters may be released in distinct regions of the cells, endowed with different populations of VSCC.